“…3D lithographic techniques provide high quality structures but are expensive and inaccessible to most researchers. , A more economical method to fabricate 3D ordered macroporous materials is by self-assembling colloids, resulting in so-called opals . A templating strategy is often used to introduce additional functionality inside the porous structure, resulting in inverse opals. ,,, Various fabrication methods for organic and inorganic inverse opals that display fluorescence, − nonlinear optics, − magneto-optics, − plasmonics, , or upconversion, − can be found in literature. Mostly, the template is first infiltrated with a solution, a sol–gel, or a melt and then removed by chemical etching or decomposition at high temperature.…”